In vivo anergized T cells form altered immunological synapses in vitro.

T cells contact allogeneic antigen presenting cells (APCs) and assemble, at their contact interface, a molecular platform called the immunological synapse. Synapse-based molecules provide directional signals for the T cell--either positive signals, resulting in T-cell activation, or negative signals causing T-cell inactivation or anergy. To better understand the molecular basis of in vivo T-cell anergy we analyzed the contacts made between in vivo anergized T cells and APCs, and determined which signaling molecules were included or excluded from their immunological synapses. Anergy was induced in TCR transgenic mice by the intravenous injection of semiallogeneic donor spleen cells. T cells from anergized mice were mixed with APCs, the T-cell/APC synapses imaged using deconvolution microscopy, and their molecular compositions were determined. T cells from anergic mice formed unstable immunological synapses in vitro with allogeneic APCs and failed to recruit the signaling proteins necessary to initiate T-cell activation. These findings suggest that T-cell anergy induced by exposure to semiallogeneic donor cells is associated with defects in the earliest events of T-cell activation, immunological synapse formation and recruitment of TCR-mediated signaling proteins.

A rare polyadenylation signal mutation of the FOXP3 gene (AAUAAA-->AAUGAA) leads to the IPEX syndrome.

The mouse scurfy gene, Foxp3, and its human orthologue, FOXP3, which maps to Xp11.23-Xq13.3, were recently identified by positional cloning. Point mutations and microdeletions of the FOXP3 gene were found in the affected members of eight of nine families with IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked; OMIM 304930). We evaluated a pedigree with clinically typical IPEX in which mutations of the coding exons of FOXP3 were not detected. Our reevaluation of this pedigree identified an A-->G transition within the first polyadenylation signal (AAUAAA-->AAUGAA) after the stop codon. The next polyadenylation signal is not encountered for a further 5.1 kb. This transition was not detected in over 212 normal individuals (approximately 318 X chromosomes), excluding the possibility of a rare polymorphism. We suggest that this mutation is causal of IPEX in this family by a mechanism of nonspecific degradation of the FOXP3 gene message.

A novel syndrome of variant leukocyte adhesion deficiency involving defects in adhesion mediated by beta1 and beta2 integrins.

Leukocyte adhesion deficiency type I (LAD-1) is a disorder associated with severe and recurrent bacterial infections, impaired extravascular targeting and accumulation of myeloid leukocytes, altered wound healing, and significant morbidity that is caused by absent or greatly diminished surface expression of integrins of the beta2 class. We report clinical features and analysis of functions of cells from a patient with a myelodysplastic syndrome and infectious complications similar to those in the severe form of LAD-1, but whose circulating neutrophils displayed normal levels of beta2 integrins. Analysis of adhesion of these cells to immobilized ligands and to endothelial cells and assays of cell-cell aggregation and chemotaxis demonstrated a profound defect in adhesion mediated by beta2 integrins indicative of a variant form of LAD-1. A novel cell line established from Epstein-Barr virus-transformed lymphoblasts from the subject demonstrated deficient beta2 integrin-dependent adhesive function similar to that of the primary leukocytes. In addition, these cells had markedly impaired beta1 integrin-dependent adhesion. Sequence analysis and electrophoretic mobility of beta1 and beta2 proteins from the cell line demonstrated that the defects were not a result of structural abnormalities in the integrin subunit chains themselves and suggest that the adhesive phenotype of these cells is due to one or more abnormalities of inside-out signaling mechanisms that regulate the activity of integrins of these classes. These features define a unique LAD-1 variant syndrome that may reveal important insights that are generally relevant to inside-out signaling of integrins, a molecular process that is as yet incompletely understood.

Growth failure, intracranial calcifications, acquired pancytopenia, and unusual humoral immunodeficiency: a genetic syndrome?

We report on two children who may represent a novel syndrome consisting of a deficiency of immunoglobulin-bearing B lymphocytes and serum antibody, deficient intrauterine and/or postnatal growth, intracranial calcifications, and acquired pancytopenia. Poor growth, intracranial calcifications, developmental delay, and hematological abnormalities are common manifestations of congenital infection. However, humoral immunodeficiency is not characteristic in these infections, and no infection was found on extensive evaluation. Rare genetic syndromes may mimic intrauterine infections and may also include immunodeficiency. However the children reported here lack important characteristics or share distinctive manifestations not described in these disorders. Infants presenting with apparent congenital infections in whom a specific infectious cause cannot be identified should be followed carefully with immunological evaluations since this disorder may be progressive and considerable morbidity is attributable to hematological and immunological manifestations.

X-Linked syndrome of polyendocrinopathy, immune dysfunction, and diarrhea maps to Xp11.23-Xq13.3.

We describe genetic analysis of a large pedigree with an X-linked syndrome of polyendocrinopathy, immune dysfunction, and diarrhea (XPID), which frequently results in death during infancy or childhood. Linkage analysis mapped the XPID gene to a 17-cM interval defined by markers DXS8083 and DXS8107 on the X chromosome, at Xp11. 23-Xq13.3. The maximum LOD score was 3.99 (recombination fraction0) at DXS1235. Because this interval also harbors the gene for Wiskott-Aldrich syndrome (WAS), we investigated mutations in the WASP gene, as the molecular basis of XPID. Northern blot analysis detected the same relative amount and the same-sized WASP message in patients with XPID and in a control. Analysis of the WASP coding sequence, an alternate promoter, and an untranslated upstream first exon was carried out, and no mutations were found in patients with XPID. A C-->T transition within the alternate translation start site cosegregated with the XPID phenotype in this family; however, the same transition site was detected in a normal control male. We conclude that XPID maps to Xp11.23-Xq13.3 and that mutations of WASP are not associated with XPID.

T lymphocytes with a normal ADA gene accumulate after transplantation of transduced autologous umbilical cord blood CD34+ cells in ADA-deficient SCID neonates.

Adenosine deaminase-deficient severe combined immunodeficiency was the first disease investigated for gene therapy because of a postulated production or survival advantage for gene-corrected T lymphocytes, which may overcome inefficient gene transfer. Four years after three newborns with this disease were given infusions of transduced autologous umbilical cord blood CD34+ cells, the frequency of gene-containing T lymphocytes has risen to 1-10%, whereas the frequencies of other hematopoietic and lymphoid cells containing the gene remain at 0.01-0.1%. Cessation of polyethylene glycol-conjugated adenosine deaminase enzyme replacement in one subject led to a decline in immune function, despite the persistence of gene-containing T lymphocytes. Thus, despite the long-term engraftment of transduced stem cells and selective accumulation of gene-containing T lymphocytes, improved gene transfer and expression will be needed to attain a therapeutic effect.

Treatment of pediatric autoimmune enteropathy with tacrolimus (FK506).

Autoimmune enteropathy is characterized by chronic secretory diarrhea, villous atrophy, associated autoantibodies, and a partial response to immunosuppression. Currently available therapy (including steroids and cyclosporine) has resulted in remission only in a subset of patients. We evaluated the effects of tacrolimus (FK506) in patients with autoimmune enteropathy refractory to steroids and cyclosporine. Three patients with diagnosed autoimmune enteropathy who continued to have intractable diarrhea despite treatment with steroids and/or cyclosporine were treated with oral tacrolimus. Despite documented histological villous atrophy and poor absorption of oral cyclosporine, therapeutic tacrolimus levels were easily achieved in all 3 patients. All patients showed clinical improvement as documented by decreased stool output and ability to be weaned off parenteral nutrition; response time ranged from 1 to 4 months after tacrolimus was begun. Histological improvement was noted in all patients, and the small bowel biopsy specimens of 2 of the 3 patients showed a return to normal. All patients have been followed up for at least 6 months and are in clinical remission; 1 has received a bone marrow transplant for underlying immunodeficiency. Tacrolimus is a useful drug in the treatment of autoimmune enteropathy, even in patients who have not responded to steroids or cyclosporine. No long-term follow-up of patients with autoimmune enteropathy treated with tacrolimus is currently available.

A single strand conformation polymorphism study of CD40 ligand. Efficient mutation analysis and carrier detection for X-linked hyper IgM syndrome.

Mutations in the gene for CD40 ligand are responsible for the X-linked form of hyper IgM syndrome. However, no clinical or laboratory findings that reliably distinguish X-linked disease from other forms of hyper IgM syndrome have been reported, nor are there tests available that can be used to confidently provide carrier detection. To identify efficiently mutations in the gene for CD40 ligand, eight pairs of PCR primers that could be used to screen genomic DNA by single strand conformation polymorphism (SSCP) were designed. 11 different mutations were found in DNA from all 13 patients whose activated T cells failed to bind a recombinant CD40 construct. The exact nature of four of these mutations, a deletion and three splice defects, could not be determined by cDNA sequencing. In addition, SSCP analysis permitted rapid carrier detection in two families in whom the source of the mutation was most likely a male with gonadal chimerism who passed the disorder on to some but not all of his daughters. These studies document the utility of SSCP analysis for both mutation detection and carrier detection in X-linked hyper IgM syndrome.

Dysgonic fermenter-3: a bacterium associated with diarrhea in immunocompromised hosts.

We describe two patients with chronic diarrhea associated with dysgonic fermenter-3 (DF-3) infection. One patient had common variable hypogammaglobulinemia and the other hand chronic idiopathic neutropenia and human immunodeficiency virus infection. Specific stool culture techniques were necessary to isolate DF-3. The organism was sensitive to clindamycin, tetracycline, and trimethoprim-sulfamethoxazole. Antibiotic therapy eradicated the organism and the diarrhea resolved in both patients. DF-3 is a little-recognized organism associated with diarrhea in the immunocompromised patient. It should be suspected when routine evaluation and stool cultures are not diagnostic.

Mechanisms of tumor necrosis factor-alpha alteration of PMN adhesion and migration.

We have investigated the effects of recombinant human tumor necrosis factor-alpha (rhTNF alpha) on polymorphonuclear leukocytes (PMNs), concentrating on the mechanisms involved in the alterations of PMN-directed migration and adherence by this cytokine. RhTNF alpha profoundly suppressed PMN chemotaxis toward FMLP by 80%. At similar concentrations, it enhanced adhesion to gelatin-coated plastic dishes by more than tenfold and increased the expression of the CD11b antigen to 182% of the control. The monoclonal antibody 60.1, which is directed against the alpha chain of the CD11b/CD18 complex, completely blocked rhTNF alpha, induced inhibition of the chemotactic response to FMLP, and rhTNF alpha induced hyperadherence, suggesting that these effects were related to rhTNF alpha's effects on CD11b antigen expression. The fluid state of the PMN membrane was also decreased by rhTNF alpha. N-butanol, a known membrane fluidizer, partially inhibited the effect of rhTNF alpha on membrane fluidity and chemotaxis and completely reversed its effects on adherence and the expression of the CD11b antigen. Pentoxifylline, an agent that has previously been studied for its ability to prevent some effects of rhTNF alpha on PMNs, completely prevented the effect of rhTNF alpha on chemotaxis, the expression of the CD11b antigen, and membrane fluidity. Pentoxifylline partially prevented changes in adherence caused by this cytokine. Increased CD11b antigen expression caused by rhTNF alpha may result in enhanced PMN adhesion and suppression of migration. These events may, in turn, lead to the accumulation of PMNs on the vascular endothelium, resulting in the extensive vascular and tissue damage that is seen in gram-negative sepsis.

Di George anomaly and velocardiofacial syndrome.

The velocardiofacial syndrome is an autosomal dominant disorder characterized by cleft palate, cardiac anomalies, characteristic facies, and learning disabilities. The Di George anomaly involves developmental defects of the third and fourth pharyngeal pouches, resulting in thymic and parathyroid hypoplasia and cardiac defects. The cases of individuals in two families help substantiate the notion that the Di George anomaly occurs as a feature of the velocardiofacial syndrome. The proband in family 1 was a male infant with persistent hypocalcemia and cardiac defects consisting of truncus arteriosus, atrial septal defect, ventricular septal defect, and abnormal aortic arch vessels. Autopsy revealed absence of thymic and parathyroid tissue, and the Di George anomaly was diagnosed. His father had a submucous cleft palate, T cell dysfunction, and facial features consistent with the velocardiofacial syndrome. This is the third case of male-to-male transmission of velocardiofacial syndrome. The proband of family 2 was a 4-year-old girl with developmental delay, persistent neonatal hypocalcemia, ventricular septal defect, T cell dysfunction, and facial features of the velocardiofacial syndrome. The Di George anomaly has been reported to occur in at least 18 different disorders. The observation that the Di George anomaly is a component manifestation of the velocardiofacial syndrome in these two families provides further evidence that the Di George anomaly is not a distinct syndrome of a single origin but rather a heterogeneous developmental field defect. It is proposed that all previously reported cases of autosomal dominant Di George anomaly are examples of the velocardiofacial syndrome.

An IgA monoclonal antibody directed against type III antigen on group B streptococci acts as an opsonin.

We have investigated the mechanisms by which a murine IgA mAb directed against the type III Ag (IgA anti-III mAb) of group B streptococci (GBS) protects neonatal rats from lethal infection with these organisms. Purified IgA anti-III mAb enhanced phagocytosis of type III GBS by rat peritoneal macrophages in vitro by fourfold compared with phagocytosis of buffer-treated GBS. In the absence of antibody, neonatal rat serum did not promote phagocytosis, but addition of neonatal rat serum to GBS opsonized with IgA anti-III led to a sevenfold increase in phagocytosis. Heat inactivation of C destroyed the ability of neonatal rat serum to enhance phagocytosis in the presence of IgA. C3 deposition was observed when GBS coated with IgA anti-III mAb were incubated in untreated neonatal rat serum or in serum treated with Mg/EGTA. This latter observation suggested that C3 deposition occurred through activation of the alternative pathway. The control IgA mAb MOPC 315 did not enhance GBS ingestion or C3 deposition on GBS. Depletion of C in vivo by using cobra venom factor abolished the protective effect of IgA anti-III mAb in the neonatal rat model. These data suggest that the ability of this IgA to activate C further enhances its opsonic activity and may be essential for its protective effect in vivo.

Intravenous immune globulin use in newborns.

Newborn infants, and especially premature ones, are uniquely susceptible to severe and overwhelming bacterial infections. The reasons for this are not completely understood. A number of defects in the neonate's host defense system have been described, including deficiency of opsonic antibodies, abnormalities in the number and function of polymorphonuclear leukocytes, and depressed levels of the major complement components. Experimental animal studies in our laboratory have indicated that many of these defects can be overcome through the administration of intravenous immune globulin. Recently several investigators have attempted to treat or prevent bacterial infections in human neonates with intravenous immune globulin. We have found that doses as high as 750 mg/kg can be administered to premature infants without detectable side effects. This results in IgG levels comparable with those in term infants and adults. Limited studies in the literature suggest that intravenous immune globulin therapy may decrease morbidity and mortality from infection in premature human infants. Furthermore, prophylactic treatment of preterm infants may serve to prevent the development of infection in some instances. Optimal management of preterm and some term human infants may involve immunotherapy with intravenous immune globulin.

Mechanisms of bacterial opsonization by immune globulin intravenous: correlation of complement consumption with opsonic activity and protective efficacy.

To study the mechanism of bacterial opsonization by immune globulin intravenous (IGIV) complement consumption and polymorphonuclear leukocyte (PMNL) membrane receptor (FcRlo, CR1, and CR3)-mediated phagocytosis of Staphylococcus epidermidis, Klebsiella pneumoniae, and groups A and B streptococci were examined. IGIV alone did not consume complement and showed no opsonic activity by itself for these organisms. When these bacteria were preopsonized in IGIV, significant amounts of complement were consumed (44%-94%) and the uptake and killing of bacteria occurred. The in vitro opsonic activity of IGIV for these organisms was significantly correlated with the amount of complement consumed by the IGIV-opsonized bacteria (r = .85, P less than .05). The in vivo protective efficacy of IGIV also appeared to be directly associated with its ability to activate and consume complement (r = 1.0, P less than .001). Antibodies to FcRlo (Leu 11) markedly inhibited phagocytosis of bacteria opsonized in IGIV but not that of bacteria opsonized in specific IgM. Both CR1 and CR3 receptors on PMNLs were involved in uptake, but the contribution of each is different with different organisms.

Neutrophil mobilization induced by complement fragments during experimental group B streptococcal (GBS) infection.

Degradation products of the third component of complement have been reported to have the ability to mobilize leukocytes from the marrow and induce leukocytosis. The effect of C3d,g preparations on neutrophil responses in a neonatal rat model of group B streptococcal infection in which neutrophil mobilization from the marrow is inadequate has been evaluated. Dimeric and monomeric fragments of C3d,g were isolated from human serum; the identity of the C3d,g preparations was confirmed by SDS-PAGE, Western blotting, and N-terminal amino acid sequencing. Uninfected neonatal rats responded to intraperitoneal injection of C3d,g with a peripheral blood neutrophilia at 30 minutes and 4 hours after inoculation. C3d,g, which lacks intrinsic chemotactic activity, enhanced the local accumulation of neutrophils in the peritoneal cavity of infected, but not uninfected, neonatal rats. In addition, myeloid cell release from the marrow of isolated femurs of neonatal rats receiving C3d,g was significantly enhanced. Thus, the effect of C3d,g in this model was to mobilize marrow cells and induce peripheral leukocytosis. Chemotactic factors released at the site of infection then resulted in the local accumulation of these inflammatory cells. Complement-derived components capable of releasing marrow myeloid elements may play a major role in determining the outcome of bacterial infection in the immature host.

Protective efficacy of IgM monoclonal antibodies in experimental group B streptococcal infection is a function of antibody avidity.

We have produced and characterized six mAb directed against group B streptococci (GBS). All antibodies are IgM. We have previously shown that some of these antibodies are highly protective in the treatment of experimental infections in neonatal rats, whereas others do not appear to have any protective efficacy. Using an ELISA, we demonstrate the specificity of both protective and nonprotective antibodies. Two antibodies, binding different epitopes, are directed against antigenic structures present on all GBS; two are specific for type III carbohydrate determinants; one binds to a protein Ag present on all type I and II GBS; and one appears to bind to type Ia GBS only. Quantitative absorption assays provide evidence that the difference between protective antibodies and nonprotective antibodies is the avidity that the antibody demonstrates for the epitope recognized on the surface of the bacteria; 10 to 15 times as much protective antibody binds to GBS as does nonprotective antibody. Direct binding experiments with radiolabeled antibody confirm this conclusion.

Correction of a developmental defect in neutrophil activation and movement.

In order to more fully understand the mechanisms involved in the developmental defect in polymorphonuclear leukocyte (PMN) movement in human neonates, the authors have examined several events in the activation response sequence. Chemotactic factor receptor numbers have been found to be normal on the PMNs of neonates, but chemotactic factor-induced changes in membrane potential and cyclic adenosine monophosphate concentrations were markedly decreased to absent in the neonatal cells. Because the neonatal PMN lacks the ability to deform normally, we examined the effects of a methylxanthine derivative, pentoxifylline, on the responses of neonatal cells. This agent has been reported to increase cell deformability and improve cell movement. Pentoxifylline had an effect in improving chemotactic function in the PMNs of neonates, while correcting the abnormality in membrane potential. In addition, this agent was found to enhance the movement of cell surface concanavalin A receptors after colchicine treatment. These results suggest that this developmental defect in cell activation and movement may be an abnormality that can be corrected pharmacologically.